1. Field of the Invention
An invention relates to an ion implanting method and apparatus for forming implanted regions with different dozes on a surface of a substrate.
2. Description of the Related Art
In recent years, there is a demand of forming implanted regions with different dose amounts on a surface of a single substrate. This is because forming such implanted regions is efficient to reduce a number of necessary substrates and steps in e.g. adjustment of an ion implanting apparatus and manufacturing semiconductor devices with different characteristics.
An example of a technique of ion-implantation to meet the above demand is described in JP-A-2000-15407.
As seen from FIGS. 12A-C, in a conventional ion implanting method by using a raster scan system of scanning an ion beam 4 in two vertical and horizontal directions (i.e. two-dimensionally), a scanning direction of the ion beam 4 is inverted around a center of a single substrate 2, and then an ion implantation is performed for each of xc2xc regions with different dose amounts on a surface of the substrate 2. The dose amounts changes in accordance with a scanning speed of the ion beam 4. Thus, four implanted regions with different dose amounts are formed on the surface of the substrate 2.
In the above conventional ion implantation technique, the scanning direction of the ion beam 4 is inverted at the center of the substrate 2. Before and after this inversion, the ion beam 4 passes processes of xe2x80x9cdecelerationxe2x80x9dxe2x86x92xe2x80x9cstoppingxe2x80x9dxe2x86x92xe2x80x9cacceleration to an opposite directionxe2x80x9d so that the scanning speed of the ion beam 4 decreases at the center of the substrate 2. Owing to this, as seen from FIG. 13, an excessively implanted region 6 is generated linearly at the center of the substrate 2.
Assuming that a diameter of the ion beam 4 in a spot shape is d0, a width W1 of the excessively implanted region 6 become certainly larger than d0.
If the above problem is solved by some methods, a transient region 8 is generated in the above conventional ion implanting method as shown in FIG. 14. The transient region is a region that dose amounts at boundaries between the implanted regions continuously changes (Herein after, referred to xe2x80x9ca transient regionxe2x80x9d).
This is because the ion beam 4 has a limited size. Assuming that the diameter of the ion beam is d0, the width W2 of the transient region 8 becomes d0.
Meanwhile, an available area which can be actually used to manufacture semiconductor devices in an entire surface of the substrate 2 is only an other area than the excessively implanted region and the transient region 8. Therefore, in order to increase the available area, the diameter d0 of the ion beam 4 must be decreased. However, when the diameter d0 is decreased, a sectional area of the ion beam 4 is decreases. As a result, a beam current of the ion beam 4 is greatly decreased. It is not practical to take a long time to process the substrate 2.
The above conventional ion implanting method adopts the raster scan system in which the ion beam 4 is scanned two-dimensionally (vertically and horizontally). However, a main trend of the present (probably so in the future) ion implanting method (apparatus) is a hybrid scan system as disclosed in e.g. JP-A-2001-143651 and JP-A-2001-185071, in which the entire surface of the substrate is subjected to ion implantation using both the electro-magnetic scanning of the ion beam and mechanical driving of the substrate. The above conventional technique cannot be applied as it is to this hybrid scan system.
Even if the concept of the above conventional ion implanting method could be applied to the hybrid scan system, both the scanning of the ion beam and a driving of the substrate must be carried out in a different manner from an ordinary hybrid scan system.
Both the devices for scanning the ion beam and for driving the substrate must be modified so that the scanning direction of the ion beam can be instantaneously changed while it is scanned and also the substrate can be driven or stopped with short steps and instantaneously in synchronism with the change of the direction of the ion beam. This makes the necessary control and mechanism complicate, and leads to high cost.
Therefore, the above modification cannot be easily realized.
It is an object of the invention to provide an ion implanting method and apparatus for forming a plurality of implanted regions with different dose amounts on a surface of a substrate.
The ion implanting method and apparatus do not make any excessively implanted region. Further, it can decrease a width of a transient region of dose amounts without decreasing a beam current. Further more, it can be easily controlled. The transient region is a region that dose amounts at boundaries between the implanted regions continuously changes (Herein after, referred to xe2x80x9ca transient regionxe2x80x9d).
In order to achieve the above objective, an ion implanting method of the present invention comprising:
implanting ions while one of a scanning speed of an ion beam and a driving speed of the substrate changes at a center of the substrate in order to separate for two implanted regions on the substrate with different dose amounts; and
rotating the substrate around its center by a predetermined angle after implanting ions while the ion beam is not applied to the substrate.
In the second aspect of the invention, the ion implanting method further comprising:
repeating by the implanting and rotation steps.
In the third of the invention, the method for implanting ions on a surface of a substrate according to claim 1, wherein implanting ions is performed by reciprocatively scanning an ion beam in an X direction by an electric field or a magnetic field and by reciprocatively and mechanically driving the substrate in a Y direction, which is substantially orthogonal to the X direction.
In the forth aspect of the invention, an apparatus for implanting ions on a surface of a substrate, the apparatus comprising:
a scanning device for reciprocatively scanning an ion beam in an X direction by an electric field or a magnetic field;
a driving device for reciprocatively and mechanically driving the substrate in a Y direction, which is substantially orthogonal to the X direction;
a rotating device for rotating the substrate around a center of the substrate;
a control device for controlling the rotating device and one of the scanning device and the driving device;
wherein the control device changes one of a scanning speed of the ion beam and a driving speed of the substrate so that ion implantation is performed to separate for two implanted regions on the substrate with different dose amounts, the control device controls the rotating device to rotate the substrate around its center by a predetermined angle after the ion implantation while the ion beam is not applied to the substrate, and the control device control to repeat the ion implantation and the rotation.
In accordance with these aspects of the inventions, since the ion implantation is implemented separately for the two implanted regions of the substrate with different dose amounts by the implanting step once performed, in combination with the rotating step, the plurality of implanted regions with different dose amounts can be formed within the surface of the substrate.
More specifically, assuming that the number of times of the implanting step is n1 (n1 is an integer of 2 or more), the number of times of the rotating step is n1xe2x88x921. By executing these implanting step and rotating step, 2n1 implanted regions with different dose amounts can be formed within the surface of the single substrate.
In addition, in these inventions, one of the scanning speed of the ion beam and the driving speed of the substrate is changed at the center of the substrate, but unlike the conventional technique, the scanning direction of the ion beam is not inverted within the surface of the substrate and the substrate is not driven and stopped with short steps while the ion beam is applied to the substrate. Namely, the ion beam does not stand still on the substrate 2 so that no excessively implanted region is formed within the surface of the substrate.
Further, when the above speed is changed, the transient region of the dose is produced within the surface of the substrate. However, the direction of changing the speed is one-dimensional (i.e. either one dimension of the X direction of scanning the ion beam and the Y direction of driving the substrate) unlike two-dimensional in the conventional technique. For this reason, by reducing the size of the ion beam in the pertinent one dimension (X direction or Y direction), the width of the transient region can be decreased. However, the size of the ion beam in the other remaining dimension is not required to be reduced, rather may be increased. Thus, reduction in the area of the ion beam can be suppressed to prevent the beam current from decreasing.
Further, the direction of changing the speed is one-dimensional as described above. In addition, the speed has only to be changed and unlike the conventional technique, the instantaneous change of the direction of the ion beam and instantaneous driving/stopping of the substrate are not required. Further, rotating the substrate as described above can be implemented itself by a known simple technique. Thus, in the case of the hybrid scan system also, the above control can be easily made and the mechanism therefor does not become complicated.
In the forth aspect of the invention, the method for implanting ions on a surface of a substrate according to claim 1, wherein implanting ions is performed by reciprocatively scanning an ion beam in an X direction and a Y direction orthogonal thereto by an electric field or magnetic field.
In the fifth aspect of the invention, an apparatus for implanting ions on a surface of a substrate, the apparatus comprising:
a scanning device for reciprocatively scanning an ion beam in an X direction and a Y direction orthogonal thereto by an electric field or a magnetic field;
a rotating device for rotating the substrate around a center of the substrate;
a control device for controlling one of the scanning device and the rotating device;
wherein the control device changes one of a scanning speed of the ion beam in the X direction and a scanning speed of the ion beam in the Y direction so that ion implantation is performed in order to separate for two implanted regions on the substrate with different dose amounts, the control device controls the rotating device to rotate the substrate around its center by a predetermined angle after the ion implantation while the ion beam is not applied to the substrate, and the control device control to repeat the ion implantation and the rotation.
These inventions also provide substantially the same effects as the inventions as described above.
In accordance with these inventions, since the ion implantation is implemented separately for the two implanted regions of the substrate with different dose amounts by the implanting step once performed, in combination with the rotating step, the plurality of implanted regions with different dose amounts can be formed within the surface of the substrate.
In addition, in these inventions, the scanning speed of the ion beam is only changed at the center of the substrate, but unlike the conventional technique, the scanning direction of the ion beam is not inverted within the surface of the substrate. Namely, the ion beam does not stand still on the substrate 2 so that no excessively implanted region is formed within the surface of the substrate.
Further, the direction of changing the scanning speed of the ion beam is one-dimension, i.e. X direction or Y direction. For this reason, by reducing the size of the ion beam in the pertinent one dimension, the width of the transient region can be decreased while reduction in the beam current is prevented.
Since the direction of changing the scanning speed of the ion beam is one-dimension as described above, and also the scanning speed is only changed, the control can be easily made. The rotation of the substrate as described above can be implemented itself by the known simple technique. Thus, the above control can be easily made and the mechanism will not be complicated.